X marks a point in the elementary analysis of fifteenth-century printing methods

Minhal Gardei (left) and Uwe Bergmann prepare a sheet of the Gutenberg Bible for digitization. Image courtesy of Minhal Gardesi

In 15th century Germany, Johannes Gutenberg developed a printing press, a machine that allowed the mass production of texts. It is considered by many to be one of the most important technological advancements of the last millennium.

Although Gutenberg is often credited as the inventor of the printing press, some time before, about 5,000 miles away, the Koreans had already developed a printing press with movable type.

There is no doubt that the East Asians were the first. There is also no doubt that Gutenberg’s invention in Europe had a far greater impact.

A paper with Chinese and Korean characters written on it.

A 19th century Asian woodblock print, with Chinese characters at the top and Korean characters at the bottom. Chinese characters are more elaborate and overlapping than Korean characters, so this print must have come from a carved block of wood, not a movable type. By scanning prints made by both metal movable type and woodcuts, researchers will be able to compare differences in techniques and possibly gain insight into the nature of the presses themselves. Image courtesy of Minhal Gardesi

“What is not known is whether Gutenberg was aware of the Korean impression or not. the University of Wisconsin-Madison who, along with UW-Madison physics graduate student Minhal Gardesi, is part of a large, interdisciplinary team that analyzes historical texts.

He adds, “But even if we don’t, we can learn a lot about early printing methods, and that will already be a great insight.”

These texts include pages from a Gutenberg Bible and Confucian texts, and they help to investigate these questions. The team includes 15th century Korean text experts, Gutenberg experts, paper experts, ink experts and many more.

An XFR is used to scan an 18th century Korean sheet. To digitize a page of text, researchers first mount it in a metal holder. The “pizza slice” device on the right is the incident beam line and the metal tube on the left detects the fluorescence.

How did two physicists end up participating in a seemingly very non-physical cultural heritage project? Bergmann had previously worked on other analyzes of historical texts, where he pioneered the application of a technique known as X-ray fluorescence (XRF) imaging.

In XRF imaging, a powerful machine called a synchrotron sends an intense, very small beam of X-rays – about the diameter of a human hair – onto a page of text at a 45 degree angle. The beam excites the electrons in the atoms that make up the text, requiring another electron to fill the space left by the first (all matter is made up of atoms, which contain even smaller components called electrons).

The second electron loses energy in the process, and this energy is released as a small flash of light. A detector placed strategically nearby captures this light, or its X-ray fluorescence, and measures both its intensity and the part of the light spectrum to which it belongs.

One of the digitized sheets printed by a Korean movable-type press in 1442. One of the UNESCO team members, Angelica Noh, traveled with the documents preserved from Korea at SLAC. Image courtesy of Minhal Gardesi

“Each element in the periodic table emits an X-ray fluorescence spectrum that is unique to that atom when struck by a high-energy X-ray. Based on its ‘color’, we know exactly which element is present,” explains Gardesi: “It’s a very high-precision instrument that tells you all the elements that are at each location in a sample.”

With this information, researchers can efficiently create an elemental map of the document. By quickly scanning a page through the X-ray beam, they can create a record of the XRF spectrum at each pixel. One page can produce several million XRF spectra.

This summer, Bergmann and Gardesi were part of a team that used XRF scanning at the SLAC National Accelerator Laboratory in California to produce elemental maps of several large areas from the original pages of a first edition of Gutenberg’s Bible. 42 lines (dating from 1450 to 1455 AD) and Korean texts dating from the first part of that. century.

They scanned the texts at a rate of about one pixel every 10 milliseconds, then filtered the data by elemental signature, providing high-resolution maps showing which elements are present and in what relative amounts.

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